LAS VEGAS (AP) — Tensions have escalated between protesters and federal police who used a stun gun on a son of a Nevada rancher fighting a roundup of cattle that he claims have historical grazing rights northeast of Las Vegas.

No serious injuries were reported and no arrests were made, but family members told the Las Vegas Review-Journal that rancher Cliven Bundy's 57-year-old sister also was knocked to the ground during a confrontation Wednesday involving dozens of protesters and several U.S. Bureau of Land Management rangers.

The son, Ammon Bundy, told the Spectrum of St. George, Utah, that he was hit with stun charges twice.

He acknowledged that he climbed on a dump truck, suspecting that it contained cattle that had been killed during the roundup.

The incident on State Route 170 followed the arrest Sunday of another Bundy son, Dave Bundy. He was released Monday with a citation accusing him of refusing to disperse and resisting arrest.

A video posted to the Internet showed protesters waving signs and shouting and law enforcement officers holding yellow stun guns with barking dogs straining at leashes near trucks involved in the roundup.

The BLM and the National Park Service have shut down an area half the size of Delaware while hired cowhands using helicopters and vehicles gather about 900 cattle that officials say are trespassing.

Bundy, whose Mormon family settled, farmed and ranched in Bunkerville since the 19th century, claims branded and feral animals on the range are his — and that he has the right to graze his cows on open range.

The showdown is seen as a flashpoint in a longstanding battle over state and federal land rights predating the Sagebrush Rebellion of the 1970s and '80s.

The government says the cows are trespassing on arid and fragile habitat of the endangered desert tortoise. They note that Bundy lost federal court cases challenging the roundup and that he was ordered by a federal judge last October not to interfere in any roundup.

Bundy, who represented himself in the court cases, has vowed to do whatever it takes to protect his property. He has characterized the dispute as a "range war."

Shows of force by heavily armed federal agents and the creation of a protest corral labeled a "First Amendment area" drew complaints this week from Republican Gov. Brian Sandoval and GOP U.S. Sen. Dean Heller of Nevada.

The tactics have also drawn attention from militia members vowing to protect Bundy and his family.

Ryan Payne and Jim Lardy, self-described members of a militia group from Montana, told the Review-Journal (http://bit.ly/1qvDREf ) that they arrived Tuesday to place themselves as a barrier between tyranny and oppression.

Bearing holstered handguns they said they always wear, Payne, 30, and Lardy, 49, said their goal was for no one to be harmed and for Bundy's property and rights to be protected.

Stephen Dean, 45, an artist from Utah, said he made the trip with a video camera in hopes of heading off another Ruby Ridge or Waco, referring to deadly confrontations involving federal agents in Idaho in 1992 and in Texas in 1993.

Photographers were on hand when BLM rangers shot Ammon Bundy several times with stun guns and Cliven Bundy's sister, Margaret Houston, said she was knocked to the ground by a BLM officer.

The Bureau of Land Management and National Park Service released a statement saying the confrontation developed when a protester crashed an all-terrain vehicle into a BLM truck driven by a contractor and protesters converged on the area.

The statement alleged that peaceful protests of the roundup that started Saturday had "crossed into illegal activity," including blocking vehicles, impeding cattle movement and "making direct and overt threats to government employees."

"These isolated actions that have jeopardized the safety of individuals have been responded to with appropriate law enforcement actions," it said.

Meanwhile, federal officials reported that 352 cows have been collected. State veterinarian and brand identification officials are expected to determine what becomes of the impounded cattle.

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